Torque wrench



Dec. 1, 1942. R, H. VAN HORN 2,303,411

TORQUE WRENCH Filed July 1l, 1939 Patented Dec. 1, 1942 UNITED STATES PATENT OFFICE 'roRQUEwRENcn y any n. van Horn, sanantonip, Tex. Application 'July 11, 1939, seal 10.283383 (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) Y 1a Claims.

' The invention describedherein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

I'his invention relates to improvementsI in torque or tension wrenches and is primarily directed to the provision, in a wrench of this type, of means for notifying or warning the operator by visual or audible signal when the nut, bolt, or other object has been tightened to a desired torque or tension.

A common object of the improvements is v,to provide aJl tension wrench of novel and generally improved construction and design characterized by simplicity and ruggedness and having many advantages over other type tension wrenches .par-

ticularly in respect to manufacturing costsV the circuit when the deflection of the handle corresponds to a desired tension.

In the drawing, I represents the head of the wrench and 2 the shank or handle portion upon which is secured the grip or handle proper 3. The wrench head is provided with jaws 4 for engaging a nut or other element to be turned and at a distance approximately one and onevquartler inches from center of opening in the jaw endiof the wrench a short at. spring E connects the head I and the shank 2. This spring provides a flexible or elastic connection between the wrench head and the wrench handle whereby l the latter is adapted to bend or be deilected from its normal position under a given load or force Y A portion of the stock adjacent the head is flattened y or reduced in cross section to form the spring 5.

The shank 2 has a dat 6 'on one side but otherwise is circular in cross section and provided with wrench of the open jaw type illustrated in the accompanying drawing, wherein: y ,E

Figure 1 is a perspective view of thel wrench; Figure 2 is a view thereof partly in elevation and partly in section;

Figure 3 is a cross section on line 3-3 of Figure 2, and v- Figure 4 is a detail view, on an enlarged scale,

of various units of the signal circuit.

Brieiiy the invention comprises a wrench, in

a distance suilcient to leave a substantial thickness of material between the cavity and the spring 5. The chambered portion of the shank serves as a housing for a signal lamp and associated parts and isl apertured at diametrical points near its open end to provide sight openings or windows 8; An elongated opening 9 for which there is a relative bending orpivotal movement between the jaw or socket and the handle whenever the device to' which the wrench is applied resists the turning force applied to the handle, and which is so constructed that the amount of spring or bend in the handle of` the wrench can be measured accurately in terms of foot pounds or other units of force applied to the boit, nut, or other device to be. tightened. The wrench is aconductor is located in the side'of the shank near the closed end` of the cavity.

"I'he lamp may be of any conventional or desired construction adapted to be enclosed in the windowed end of the cavity "I so as to be visibleL through the windows 8. A suitable construction comprises a small glass bulb I0 secured at its lower portion within an encircling ring or band II of metal to which is electrically connected one end of the lamp lament. The bulb and conductor are mounted in a metallic holder comprising a. socket I2 in which the bulbi/and conductor are fixed and abase disk or flange I3 to which i the other end of the lamp lament is electrically provided with electric signaling means including erated by the `movement of the handle to close,

connected; the holder and conductor ring insulated one from the other. The outside diameter of the socket is such that it hasv a snug sliding t in the end of a tube I4 of insulation material with which the cavity 'I is lined. An attenuated dome or cover I5 of thin metal has a snug t 0n the insidei'f. the .insulating tube I!" and 1S l anchored in place by a short, covered, conductor wire I6 extending through the elongated opening 9 of the shankA and secured at one end to the dome I and at the other end to the4 member I'I as shown in Figure 2. When the lamp is inserted in the open end of the shank, the conduc-y tor band I I is telescoped by the open endv of the dome which thus serves as an electrical conductor between the band and the covered wire. The tube I4 andthe dome I5 are suitably apertured in line with the windows 8 so as not to obstruct the view to the. lamp.

For the size wrench shown, a small 2 volt electric lamp is used and the required voltage is supplied by two small flash light batteries I8 of 1 volt each. These are contained in thev handle 3 which is a hollow barrel or cylinder internally screw threaded at one end to receive the threaded shank 2 and externally threaded at its opposite end to receive a screw cap I9.

The two batteries are arranged in tandem with the foremost battery held'in electrical contact with the base I3 of the lamp by thepressure of a spring 20 between the outermost battery and the cap. 'I'he handle 3 has. a tubular lining 2l of insulating material and also windows 22 in line with windows 8 of the shank,

Integral with the head I and extending out.- wardly thereof and over relatively opposite sides of the spring 5 are two curved horn-like projections 23 constituting one set of switch points or contacts. Another set of switch points or contacts comprises two rods 24 mounted in th*- member II which has a collar encircling the shank 2 between the handle 3 andthe spring 5. The collar is insulated from the shank by a. two-part flanged sleeve bushing 25 of insulating material but is electrically connected, by solder or otherwise, to the conductor wire I6. Collar I'I and insulating bushing 25 have a slide t on the threaded shank 2 and are held against longitudinal displacement from a given position by means of front and rear lock nuts 26. Each bushing is provided with inner and outer lplane faces or iiats; the inner flats 21 being adapted to cooperate with the fiat side B of the shank 2 to.

prevent turning of the bushings on the shank, and the outer flats 28 being adapted to cooperate with a. nat (not shown) in the bore of the collar I1 to prevent any rotation between the bushing and the collar. These iiats are so corelated with the opposed sets of contactpoints 23 and 24 as to insure proper alignment of the points when assembling and using the wrench.

Contact points 23 are electrically connected to one terminal of thelamp filament by the shank4 2, barrel 3, cap I9, spring 20, batteries I8, and lamp base4 I3. Contact points 24 are electrically connected to the other terminal of the lamp filament by the collar I1, wire I6, dome I5, and conductor ring II. Points 23 and 24 normally are spaced apart to provide a gap or break in the signal circuit and the length ofgap determines the amount of bent or deflection o1 the handle required to move the points on one or the other side of the wrench together closing the gap and completing the circuit. In order that the size of the gap maybe varied, the contact rods 24 are made adjustable. To this end, the rods have a slide bearing on` the smooth bores of cylindrical bearing lugs 29 forming integral parts oi' the collar Il on relatively opposite sides thereof as shown. Nuts 30 are screwed on opposite ends of the rods for adjusting and locking the rods in' position. Each rod carries a pointer 3l working in a longitudinal slot 32 in its respecA tive bearing lug and reading against scale marks 33 calibrated to indicate the torque or tension, placed on the nut or bolt in the tightening operation, corresponding to various degrees of deflectionv of the wrench handle. The scale may be calibrated in inch pounds, foot pounds; or other desired and appropriate units of measurement..

In use, the points 24 are adjusted untilthe pointers are opposite the scale marks correa4 sponding tothe maximum torquel or tension ac cording to which the nut or other element is to be tightened. The wrench is applied to the nut and. turned in the usual manner by pressure exerted on the handle. 'As the nut tightens,` the resistance thereof to the turning oi the wrenchv increases proportionately and when this resistance. exceeds the strength of thespring, the handle of the wrench bends at this place. The deflection of the handle from its normal position exes or tensions the spring to exert an increased', torque on thelnut proportionate to the bending; or deflection of the handle. When the deflection is such that one or the other paired contact points 23 and 24 engage the signal circuit is, closed and the signal lamp is lighted, indicating that a desired tension has. been reached. The operator can tell by the ilash of light when the desired tension has been attained -even though the position of the wrench is such that a direct view of the indicator is impossible.

The accuracy required toobtain the proper tension on small bolts used in aircraft construction can only be lobtained by .a sensitive tension r wrench. By utilizing the electric light and contact points with the principle developed in the subject wrench, this accuracy can be obtained within the limit of one pound or.less. The difculty encountered in aircraft construction particularly, i. e. working in close places, necessitates the use of small compact wrenches. The design and construction of this wrench is such that it will meet these requirements. Y

Having thus described the invention, I claim: 1. In a leverage indicating device, in combination, a lever attened for a portion of its length and inwardly of its ends to provide a thin flexible section between thick rigid outer sections, said `flexible section being adapted to bend under a ed to contact each other-'across the flexible sec- Y tion at a pre-selected relative deflection of the rigidA sections whereby to close the said circuit.

2.v In 'a leverage indicating device, a lever having a ilexible elastic portion adapted to bend under a predetermined stress and through an angle which is proportional to the torque or leverlage, arid a normally opened signal circuit includingcircuitclosing elements mounted on the lever adjacent each end of the bendable portion, the elements at one end of the bendable portion being complementary to and spaced from corresponding elements at the other end oi the said bendable portion and adapted to be moved into contact therewith by the bending of the lever through a pre-selected angle to close the circuit,

said circuit closing elements being manually settable to close the circuit at any desired angle within the bending range of the lever.

3. An electric indicating torque 'wrench vcomprising a head and a shank forming integral parts of a single piece of comparatively thick rigid stock reduced in cross section at the junction of the head and'shank to provide a thin flat elastic portion bendable under a given stress to permit deflection ofthe shank from a normal position with respect to the head, and an electric signal circuit including a signal member carried by the shank and co-operating circuit controlling con- 'tacts mounted on the head and shank respectiveon the shank near its free end and co-operating circuit controlling contacts mounted on thev wrench at opposite sides of the bendable portion to be moved into and out ofmutual engagement by a predetermined deection and return of the shank with respect to its normal position, said contacts being adjustable to cause the circuit to be closed at any desired tension within the range of the wrench corresponding to a given deflection of the shank.

5. A torque wrench comprising a head adapted to be engaged with an element to be turned, a shank having a exible connection with the head portion whereby the shank portion is adapted to be deected with respect to the head portion under a predetermined applied torque, handle and a set of contact points operatively connected to vthe said head portion and extending laterally therefrom and over relatively opposite side faces of the spring portion, a set of contact points carried by and insulated from the shank portion for engagement with the contact points of the head portion, means for maintaining the points of one s et in alignment with corresponding points of the other set, said sets being spaced apart to provide in the absence of applied torque an air gap between corresponding contact pointsy and adapted to be electrically connected when the deilection of the shank is such as to close the gap between corresponding points, and a signal lamp in the chamber of the shank and electrically connected to thevsets of contact points.

3 connection between the said inflexible members whereby it is adapted to be deflected from a normal position with-respect to the head under a given force applied to the handle when turning the said element, a chambered handle secured to the shank and having windows therein, a lamp in said handle and visible through the windows, a battery in said handle, a set of contact points on the said head and extending rearwardly over the flexible connection, and another set of contact points on the said shank and extending forwardly over the iiexible connection in line with the first set to be engaged therewith by a deiiection of the shank to close an electrical circuit through the lamp, one set of points being electrically and directly connected to one terminal of the battery and the other set being electrically connected through the lamp tothe other terminal of the battery.

6. A torque wrench comprising a lever consisting of thick head and shank portions integrally connected by a substantially flat thin spring portion adapted to be flexed by a deection of the shank, a pair of contact points fixedto said head on opposite sides thereof and projecting o ver the said spring portion, a pair of contact points on the said shankand adjustable to be lined up with xed contact points for engaging the latter at a preselected deflection of the said shank, a

adapted to.be exed by force applied thereto through the handle member, electrical signal means, electrical contact elements arranged in circuit with the signal means and operatively associated with the said members whereby a contact element associated with one of the members handle member, a'substantially short straight at spring connected at one end rigidly to the Work-engaging member and at the other endl rigidly to the handle member to provide a exible elastic connection between and serving to longitudinally space apart the said members whereby the latter are adapted to be deflected lrelative to one another about an axis located between the lrigidly connected ends of the spring electrical signal means, contact elements associated with the handle and extending forwardly beyond the spring-connected end thereof and on relatively opposite sides of .the'spring, means in circuit with the signal means-and associated 'with the workengaging member to extend rearwardly of its spring-connected end to engage the contact yelements 'of thehandle member to close the circuit to the signal means when the latter member is deflected a predetermined amount.

10. A torque indicating wrench comprising an inflexible work-engaging member, an inexible handle member, a short double concave spring rigidly connected at one end to the work-engaging member and rigidly connected at its other end lhandle member respectively to be moved into th critical positionA by and upon a predetermined deection of the spring.

11. A torque indicating wrench comprising a Lwork-engaging member, a handle member, a

short double concave spring connected at one end rigidly to the work-engaging member and at the other end rigidly to the handle member to provide a exible elastic connection between and serving disposed jaw portion and a rearwardly disposed shank portion integrally connected therewith and a pair of curved horn-like projections integrally connected with the jaw portion adjacent the junction of the latter with the 4shank portion and 'extending outwardly therefrom and rearwardly over the shank on relatively opposite sides of the member, said shank portion being reduced in cross section over a small area adjacent the jaw portion to provide a short flexible elastic section adapted to be ilexed under a given load applied to the shank portion, electrical signal means arranged in circuit with the said projections, means associated with the shank portion and arranged beyond the flexible section thereof to engage the said projections when the 'said section has been exed a predetermined amount to thereby close the circuit for operating the signal means, and a handle on the said shank portion.

- ROY H. VAN HORN. 

